Morphine Protects Spinal Cord Astrocytes from Glutamate-Induced Apoptosis via Reducing Endoplasmic Reticulum Stress

Glutamate is not only a neurotransmitter but also an important neurotoxin in central nervous system (CNS). Chronic elevation of glutamate induces both neuronal and glial cell apoptosis. However, its effect on astrocytes is complex and still remains unclear. In this study, we investigated whether morphine, a common opioid ligand, could affect glutamate-induced apoptosis in astrocytes. Primary cultured astrocytes were incubated with glutamate in the presence/absence of morphine. It was found that morphine could reduce glutamate-induced apoptosis of astrocytes. Furthermore, glutamate activated Ca2+ release, thereby inducing endoplasmic reticulum (ER) stress in astrocytes, while morphine attenuated this deleterious effect. Using siRNA to reduce the expression of κ-opioid receptor, morphine could not effectively inhibit glutamate-stimulated Ca2+ release in astrocytes, the protective effect of morphine on glutamate-injured astrocytes was also suppressed. These results suggested that morphine could protect astrocytes from glutamate-induced apoptosis via reducing Ca2+ overload and ER stress pathways. In conclusion, this study indicated that excitotoxicity participated in the glutamate mediated apoptosis in astrocytes, while morphine attenuated this deleterious effect via regulating Ca2+ release and ER stress

Galnon Facilitates Extinction of Morphine-Conditioned Place Preference but Also Potentiates the Consolidation Process

Learning and memory systems are intimately involved in drug addiction. Previous studies suggest that galanin, a neuropeptide that binds G-protein coupled receptors, plays essential roles in the encoding of memory. In the present study, we tested the function of galnon, a galanin receptor 1 and 2 agonist, in reward-associated memory, using conditioned place preference (CPP), a widely used paradigm in drug-associated memory. Either before or following CPP-inducing morphine administration, galnon was injected at four different time points to test the effects of galanin activation on different reward-associated memory processes: 15 min before CPP training (acquisition), immediately after CPP training (consolidation), 15 min before the post-conditioning test (retrieval), and multiple injection after post-tests (reconsolidation and extinction). Galnon enhanced consolidation and extinction processes of morphine-induced CPP memory, but the compound had no effect on acquisition, retrieval, or reconsolidation processes. Our findings demonstrate that a galanin receptor 1 and 2 agonist, galnon, may be used as a viable compound to treat drug addiction by facilitating memory extinction process

PtrARF2.1 Is Involved in Regulation of Leaf Development and Lignin Biosynthesis in Poplar Trees

Auxin response factors (ARFs) are important regulators modulating the expression of auxin-responsive genes in various biological processes in plants. In the Populus genome, a total of 39 ARF members have been identified, but their detailed functions are still unclear. In this study, six poplar auxin response factor 2 (PtrARF2) members were isolated from P. trichocarpa. Expression pattern analysis showed that PtrARF2.1 is highly expressed in leaf tissues compared with other PtrARF2 genes and significantly repressed by exogenous auxin treatment. PtrARF2.1 is a nuclear-localized protein without transcriptional activation activity. Knockdown of PtrARF2.1 by RNA interference (RNAi) in poplars led to the dwarf plant, altered leaf shape, and reduced size of the leaf blade, while overexpression of PtrARF2.1 resulted in a slight reduction in plant height and the similar leaf phenotype in contrast to the wildtype. Furthermore, histological staining analysis revealed an ectopic deposition of lignin in leaf veins and petioles of PtrARF2.1-RNAi lines. RNA-Seq analysis showed that 74 differential expression genes (DEGs) belonging to 12 transcription factor families, such as NAM, ATAF and CUC (NAC), v-myb avian myeloblastosis viral oncogene homolog (MYB), ethylene response factors (ERF) and basic helix–loop–helix (bHLH), were identified in PtrARF2.1-RNAi leaves and other 24 DEGs were associated with the lignin biosynthetic pathway. Altogether, the data indicate that PtrARF2.1 plays an important role in regulating leaf development and influences the lignin biosynthesis in poplars

Effect of galnon on consolidation of morphine-induced CPP.

<p>A, Behavioral procedure for injection time points in consolidation process. Upward arrows indicates galnon or saline injection. B, Galnon enhanced the consolidation process of morphine-induced CPP. C, Behavioral procedure for time points of locomotor activity tests after post-training injection of 10 mg/kg galnon. Down arrows indicate galnon or saline injection. D, The locomotor activity in two training days did not be influenced by post-training injection of 10 mg/kg galnon. ^∧<i>p</i><0.05 vs morphine-saline group; * <i>p</i><0.05 vs saline-saline group in each test.</p

Effect of galnon on acquisition of morphine-induced CPP.

<p>A, 10/kg galnon injection impaired the locomotor activity. B, Galnon itself had no effects of CPP and CPA. C, Behavioral procedure for injection time points in acquisition process. Upward arrows indicate galnon or saline injection. D, The acquisition process of morphine-induced CPP did not be influenced by galnon. ^@<i>p</i><0.05 vs the other groups; * <i>p</i><0.05 vs saline-saline group in each test.</p

Effect of multiple post-retrieval galnon injections on expression of morphine-induced CPP.

<p>A, Behavioral procedure for mutiple post-retrieval galnon injections. Upward arrows indicate galnon or saline injection. B & C, Galnon facilitated CPP extinction, but did not impair the reinstatement of morphine priming, though 10 mg/kg galnon had stronger effect for the quickly recovering and maintaining of extinction-effect after priming. D, The time points of the disappearing CPP-effect in morphine-saline group. # <i>p</i><0.05 morphine-saline vs saline-saline, * <i>p</i><0.05 morphine-galnon5 or morphine-galnon10 vs saline-saline, $ <i>p</i><0.05 vs saline (sal) priming day test.</p